Sidescan sonar imagery of widespread fossil and active cold seeps along the central Chilean continental margin
The central Chilean subduction zone between 35°S and 37°S was investigated in order to identify, document and possibly understand fluid flow and fluid venting within the forearc region. Several areas were mapped using multibeam bathymetry and backscatter, high-resolution sidescan sonar, chirp subbottom profiling and reflection seismic data. On a subsequent cruise ground-truthing observations were made using a video sled. In general, this dataset shows surprisingly little evidence of fluid venting along the mid-slope region, in contrast to other subduction zones such as Central America and New Zealand. There were abundant indications of active and predominantly fossil fluid venting along the upper slope between 36.5°S and 36.8°S at the seaward margin of an intraslope basin. Here, backscatter anomalies suggest widespread authigenic carbonate deposits, likely the result of methane-rich fluid expulsion. There is unpublished evidence that these fluids are of biogenic origin and generated within the slope sediments, similar to other accretionary margins but in contrast to the erosional margin off Central America, where fluids have geochemical signals indicating an origin from the subducting plate.
- Geersen J, Völker D, Krastel-Gudegast S, Diaz J, Weinrebe RW, Behrmann JH (2011) Active tectonics of the South Chilean marine forearc (35°S – 40°S). Tectonics 30:TC3006. doi:10.1029/2010TC002777
- Greinert J, Bohrmann G, Suess E (2001) Gas hydrate-associated carbonates and methane-venting at Hydrate Ridge: classification, distribution and origin of authigenic lithologies. In: Paull CK, Dillon PW (eds) Natural gas hydrates: occurrence, distribution, and detection. AGU Geophys Monogr 124:99–113Google Scholar
- Greinert J, Lewis K, Bialas J, Pecher I, Rowden A, Linke P, De Batist M, Bowden D, Suess E (2010) Methane seepage along the Hikurangi Margin, New Zealand: review of studies in 2006 and 2007 and new evidence from visual, bathymetric and hydroacoustic investigations. Mar Geol 272:6–25CrossRefGoogle Scholar
- Kukowski N, Oncken O (2006) Subduction erosion—The “normal” mode of fore-arc material transfer along the Chilean Margin? In: Oncken O, Chong G, Franz G, Giese F, Götze H-J, Ramos VA, Strecker ME, Wigger P (eds) The Andes: active subduction orogeny. Springer, Berlin, pp 217–236Google Scholar
- Ranero CR, Grevemeyer I, Sahling H, Barckhausen U, Hensen C, Wallmann K, Weinrebe RW, Vannucchi P, von Huene R, McIntosh K (2008) The hydrogeological system of erosional convergent margins and its influence on tectonics and interplate seismogenesis. Geochem Geophys Geosyst 9:Q03S04. doi:10.1029/2007GC001679 CrossRefGoogle Scholar